eheim 2228 problem

[trapper]

Hi there. I have just got a new 6 ft tank and cannot wait to set it up .. but I am having a problem with my eheim 2228 filter which is second hand and the magnetic center bit that spins around has hard crud or crystilized bits .. it keeps cutting out consistently ... I have gone in and cleaned it throughly ... Does anyone know where I can buy a the top bit for this filter with the working bits. thanking you in advance
Joe Trapper